Alkaline batteries have become increasingly more popular because of their high energy density. As such, these batteries are increasingly used in applications normally reserved for the traditional lead-acid battery systems.
In order to achieve extended battery life and efficiency in alkaline systems, the use of battery separators is required and the use of battery interseparators, as well, is preferred. The battery separators are located between the positive and negative plates so as to provide, (1) a separation between the electrodes of opposite charge, (2) an electrolyte reservoir, (3) a uniform electrolyte distribution across the electrode surface so as to permit uniform current density and (4) a space for electrode expansion.
Battery separators and interseparators used in alkaline batteries at present are commonly formed of a polyolefin, preferably polypropylene, polyamide or nylon non-woven sheet.
Other separators in use in alkaline systems today are shown in U.S. Pat. Nos. 4,264,691 and 4,330,602 in which the separator/interseparator is formed of synthetic pulp, alkali resistant inorganic filler and a long fiber of polyester, polyacrylic, polyamide or polyolefin materials. Another type of separator is a microporous plastic film such as is described in U.S. Pat. No. 3,351,495.
Until now, these separators have been suitable for existing technology.
Battery makers now require a separator with better performance characteristics than is currently available with the current separators, especially those based upon nylon or treated polypropylene. Preferably, they desire greater and faster wettability of the separator by the alkaline electrolyte.
The present invention overcomes the problems inherent in the currently used separators and provides a wettable sheet material with the desired tensile strength, chemical inertness, electrolyte absorption and electrical resistance properties which is usable in alkaline batteries.